Support media with supported object

ABSTRACT

Pellicles of para-xylylene polymers are used as the sole support media for masses of objects supported thereon. The supported objects can be combined with the pellicle either during the formation of the pellicle or after the pellicle has been manufactured. The composite article is used wherever it is desirable to provide a support media which has as little detrimental influence as possible on the intended function of the supported object.

ilmted States Patent 1191 1111 3,864,202 Loeb et a1. 1 1 Feb. 4, 1975[54] SUPPORT MEDIA WITH SUPPORTED 3,429,739 2/1969 Tittman et a1.117/106 OBJECT 3,600,216 8/1971 Stewart 117/106 3,764,455 10/1973 Lovellet a1 117/33 [75] Inventors: William E. Loeb, Martinsville; Mark A.Spivack, Wachtung, both of N]. E h Primar xaminer-C arles E. Van Horn[73] Assignee: Union Carbide Corporation, New Asst-stair Massie YorkAttorney, Agent, or Firm-James J. OConnell [22] Filed: May 24, 1972 21 Al. N 256,531 1 pp 0 57 ABSTRACT Related US. Application Data [62]Division of Ser. No. 167,252, July 29, 1971, Pellicles of para-xylylenepolymers are used as the sole abandoned. support media for masses ofobjects supported thereon. The supported objects can be combined with[52] US. Cl 161/162, 117/37, 161/168, the pellicle either during theformation of the pellicle 248/346 or after the pellicle has beenmanufactured. The com- [51] Int. Cl B32b 19/02 posite article is usedwherever it is desirable to pro- [58] Field of Search 117/227, 106 R,37, 33, vide a support media which has as little detrimental 117/26;161/162, 168; 156/622; 250/456; influence as possible on the intendedfunction of the 248/346 supported object.

[56] References Cited 10 Claims, 4 Drawing Figures UNITED STATES PATENTS3,301,707 1/1967 Loeb et a1 117/227 SUPPORT MEDIA WITII SUPPORTED OBJECTThis patent application is a division of application Ser. No. 167,252filed July 29, 1971, now abandoned.

BACKGROUND OF THE INVENTION SUMMARY OF THE INVENTION It has now beenfound that para-xylylene polymers can be used as innocuous support mediafor the purposes of supporting thereon an active or passive device ormaterial if extremely thin films or pellicles of the para-xylylenepolymer are used as the support media.

An object of the present invention is to provide innocuous support mediafor active or passive articles which are to be supported on said media.

BRIEF DESCRIPTION OF THE DRAWINGS FIGS. 1 to 3 show a simulated dustfield supported on a pellicle. FIG. 4 shows an electron beam masksupported on a pellicle.

DESCRIPTION OF THE PREFERRED EMBODIMENT In accordance with the preferredteachings of the present invention pellicles of p-xylylene polymers areused as innocuous support media to wholly support thereon active orpassive masses. These mass es may be incorporated into the pellicleeither during the formation of the pellicle or after the pellicle hasbeen manufactured.

The expression wholly supporting" means that the poly-paraxylylenepellicle is the sole support for the objects supported thereon, and, inthe plane of the film, the object is completely surrounded by such film.Because of the resulting geometric isolation of the pellicle supportedobjects, relative to any other objects not so supported by the pellicle,the supported objects are rendered ohmically isolated from suchnon-supported objects.

The Pellicles The pellicles which are used as the innocuous supportmedia for the purposes of the present invention are essentially flatfilms of para-xylylene polymers which have a thickness of up to about25,000, and preferably in the range of about 250 to 5,000, angstromunits. These films have a mass of up to about 400, and preferably in therange of about 2.5 to 75, micrograms per square centimeter. Thesepellicles, for the purposes of the present invention, have a totalsurface area, on each face thereof, of about a 25 square millimeters,and preferably of about 100 to 500 square centimeters.

The mass of a pellicle will vary depending on the thickness of the filmsand the density of the polymer which is used to form the film. Theparaxylylene polymers which are used to form the films have densities ofthe order of about 1.0 to 1.5.

The term essentially flat means that the free film, when observed undermonochromatic light in the visible region will exhibit s 4 interferencefringes in any given square centimeter of surface area on the surface ofthe pellicle.

The films or pellicles of the'para-xylylene polymers are prepared, asdisclosed in the above mentioned patents, by condensing vapors ofp-xylylene monomer which can be produced by the pyrolytic cleavage ofone or more cyclic dimers represented by the following structure whereinR is an aromatic nuclear substituent, x and y are each integers from 0to 3, inclusive, and R is H, Cl and/or F. The thus formed vaporousmonomers may be in the form of diradicals having the structures and/ormoieties having the tetraene or quinoid structures:

and

It is believed that the tetraene or quinoid structure is the dominantstructure which results when the dimer is pyrolyzed, but that themonomer polymerizes as though it were in the diradical form.

Thus, where x and y are the same, and the aromatic nuclear substituenton each monomer is the same, and all the Rs are the same, two moles ofthe same pxylylene monomer are formed, and when condensed, yield asubstituted or unsubstituted p-xylylene homopolymer. When x and y aredifferent or the aromatic nuclear substituents on each monomer aredifferent, or the R's are different, condensation of such monomers willyield copolymers as hereinafter set forth. Examples of the R substituentgroups which may be present in the dimers and monomers are organicgroups such as alkyl,

- aryl, alkenyl, cyano. alkoxy, hydroxy alkyl, carbalkoxy naphthyl andlike groups; and the halogen groups, chlorine, bromine, iodine andfluorine. Hereinafter the term a di-p-xylylene refers to any substitutedor unsubstituted cyclic di-p-xylylene as hereinabove discussed. v

Condensation of the monomers to form the pxylylene polymers can beaccomplished at any temperature below the decomposition temperature ofthe polymer, i.e., at 250C. The condensation of the monomers willproceed at a faster rate. the colder is the substrate on which thecondensation is to take place. Above certain temperatures, which mightbe defined as a ceiling condensation temperature, the monomers will onlycondense at rates which are relatively slow for commercial applications.Each monomer has a different ceiling condesation temperature. Forexample, at 0.5 mm Hg pressure the following condensation andpolymerizations ceilings are observed for the following monomers:

Degrees centigrade p-Xylylene -30 Chloro-p-xylylene 70-80 Cyano-p-xylylene l 20-1 n-Butyl-p-xylylene l 30- I Iodo-p-xylylene180-200 Thus, homopolymers may be made by maintaining the substratesurface at a temperature below the ceiling homopolymerization willresult when the condensation and polymerization temperature is selectedto be at or below that temperature at which only oneofthe monomerscondenses and polymerizes. Thus, for the purposes of this invention theterm under homopolymerization conditions is intended to include thoseconditions where only homopolymers are formed.

Therefo-re'it is possible to make homopolymers from an mixturecontaining one or more of the substituted monomers when any othermonomers present have different condensation or vapor pressurecharacteristics, and'wherein only one monomer species is condensed andpolymerized on the substrate surface. Of course, other monomer speciesnot condensed on the substrate surface can be drawn through theapparatus as hereinafter described in vaporous form to be condensed andpolymerized in a subsequent cold trap.

Inasmuch as the p-xylylene monomers, for example, are condensed attemperatures of about 25 to 30C., which is much lower than that at whichthe cyano pxylylene monomers condense, i.e., about l20 to l30C., it ispossible to have such p-xylylene monomers present in the vaporouspyrolyzed mixture along with the cyano-substituted monomers when ahomopolymer of the substituted dimer is desired. in such a case,homo-polymerizing conditions for the cyano p-xylylene monomers aresecured by maintaining the substrate surface at a temperature below theceiling condensation temperature of the substituted p-xylylene but abovethat of the unsubstituted p-xylylene, thus permitting the unsubstitutedp-xylylene vapors to pass through the apparatus without condensing andpolymerizing, but collecting the poly-p-xylylene in a subsequent coldtrap.

It is also possible to obtain substituted copolymers through thepyrolysis process hereinabove described. Copolymers of p-xylylene andsubstituted p-xylylene monomers, as well as copolymers of substitutedpxylylene monomers wherein the substituted groups are all the sameradicals but wherein each monomer contains a different number ofsubstitutent groups, can all be obtained through such pyrolysis process.

Copolymerization also occurs simultaneously with condensation, uponcooling of the vaporous mixture of reactive monomers to a temperaturebelow about 200C. under polymerization conditions.

Copolymers can be made by maintaining the substrate surface at atemperature below the ceiling condensation temperature of the lowestboiling monomer desired in the copolymer, such as at room temperature orbelow. This is considered copolymerizing conditions, since at least twoof the monomers will condense and copolymerize in a random copolymer atsuch temperature.

In the pyrolytic process, the reactive monomers are prepared bypyrolyzing a substituted and/or unsubstituted dipara-xylylene at atemperature less than about 750C., and preferably at a temperaturebetween about 600C. to about 680C. At such temperatures, essentiallyquantitative yields of the reactive monomers are secured. Pyrolysis ofthe starting di-p-xylylene begins at about 450 C. regardless of thepressure employed. Op-

eration in the range of 450-550C. serves only to increase the time ofreaction and lessen the yield of polymer secured. At temperatures aboveabout 750C.,

cleavage of the substituent group can occur, resulting in a tri-lorpolyfunctional species causing cross-linking or highly branchedpolymers.

The pyrolysis temperature is essentially independent of the operatingpressure. It is preferred, however that reduced or subatmosphericpressures be employed. For most operations, pressures within the rangeof 0.0001 to mm. Hg absolute are most practical. However, if desired,greater pressures can be employed. Likewise, if desirable, inertvaporous diluents such as nitrogen, argon, carbon dioxide, steam and thelike can be employed to vary the optimum temperature of operation or tochange the total effective pressure in the system.

When the vapors condense on the substrate to form the polymer, thepolymer forms as a continuous film of uniform thickness. The films aretransparent and pinhole free. The surface area and thickness of the filmcan be varied by various procedures, as by varying the size of thesubstrate, by varying the amount of dimer used, and by varying thereaction temperature, time and pressure.

The Supported Masses The masses which are to be supported on theparaxylylene films may be active or passive devices or objects. The thussupported devices or objects are used where it is desirable that theaction of the support medium has as insignificant an influence aspossible on the intended function of the supported active or passivedevice or object. The para-xylylene polymer pellicles, therefore, areused as relatively massless, non-existant positioning media, such thatany detrimental effect of various types of influences such as thermalinfluences, mass and gravitational influences, radiated energy types ofinfluences and magnetic or electrostatic field influences due to thepellicle is insignificant while the supported article or object performsits intended function relative to such influences.

Examples of passive objects or devices which may be supported onpellicles are droplets of encapsulated fluid such as water, or particlesof sand or glass which may be deposited or used on the para-xylylenepolymer films in order to simulate dust fields, ice fields, and rainfields. These simulated dust fields, ice fields and rain fields are usedas a means for measuring the amount of erosion which a natural dustfield, ice field or rain field might cause when a ballistic vehicle isfired or passed through such fields. Thus, the simulated dust fields,ice fields or rain fields can be prepared by placing particles of sandor glass or encapsulated fluids on the pellicles and mounting the thussimulated field in the path of a simulated ballistic missile andphotographing or otherwise monitoring the impact of the missile on thesimulated field, and by measuring the amount of erosion on the ballisticmissile which the simulated field causes. When the simulated dust or icefields are prepared, they are usually prepared in such a way as to havethe supported particles of simulated dust or ice cover up to about 10%of the supporting surface of the pellicle. When the simulated rainfields are prepared, they are usually prepared in such a way as to havethe supported droplets of encapsulated liquid which is used to simulatethe rain cover up to about 80% of the supporting surface of thepellicle. The particles of liquid can be encapsulated in poly-p-xylyleneor other known agents for encapsulating droplets of liquids. Thedroplets or particles which are used for the purposes of simulating thedust, ice or rain usually have a diameter of up to about 5 mm, andpreferably of about 0.05 to 2 mm. The

supported particles may be mounted on the pellicles in an ordered orrandom pattern. The pellicles on which these simulated dust, ice or rainfields are mounted usually have a surface area, on each face thereof, ofabout 300-400 square centimeters.

Examples of the active types of devices or objects which may be mountedon the para-xylylene polymer pellicles of the present invention aredevices or objects which are adapted to absorb, transmit, and/or reflectradiated energy in a perceptible manner. Examples of electromagneticradiation which may be encountered in this regard include gamma rays,X-rays, infrared rays, ultraviolet light rays, radio rays, visible lightrays and electrons. These types of radiation usually have a wave lengthof at least 10' meters, and preferably a wave length of about 10 to 10*meters. In the case of ionizing radiation, the preferred range of energyvalues is 2 0.01 Kev (kilo electron volt). These types of devices orobjects include those which are more opaque to the electromagneticradiation than is the para-xylylene polymer film and which may be usedin mounted form as masks for the radiation beams, such as electron beammasks. These masks provide a pattern for the radiated energy wherein theradiated energy can be transmitted in some areas and be absorbed orreflected in other areas.

Another type of the active devices or objects which may be mounted onthe pellicles are those which are adapted to absorb and perceptiblyrespond to mechanical energy,.such as sound waves or thermal energy,such as bimetallic strips for sensing temperature changes. A furthertype of the active device or object which may be mounted on the pellicleare those which are adapted to sense and perceptibly respond to amagnetic field, and these would include all magnetisable materials.

A further type of active device or object which may be mounted on thepellicles are those which are adapted to sense and perceptibly respondto an electrostatic field such as a capacitive device.

When these active type of devices or objects are mounted on the surfaceof the pellicles they are mounted in such a way as to cover up to aboutand preferably about 0.5 to 75%, of the surface of the pellicle on whichthey are mounted. They are usually mounted or positioned on thepellicles in an ordered manner. The pellicles on which these activetypes of devices or objects are mounted have surface areas in the rangeof 3 to square centimers.

It may be seen, therefore, that the interaction of the supportingpellicle is insignificant when compared to the action of the suspendeddevice or object which is supported on the pellicle. Also, because ofthe nature of the pol y-para-xylylene materials they are not perceptiblyinfluenced by the other forces which may be directed against thesupported device or object such as thermal influences, magneticinfluences, electrostatic influences, and electromagnetic radiationinfluences. Thus, the pellicle acts almost as an invisible ornonexistant support medium for the purposes of subjecting the supportedobject or device to a specific influence without having the supportmedia either contribute to such influence or be affected by suchinfluence.

The devices or objects may be mounted or supported on the pellicle byeither embedding them in one or both of the faces of the pellicle or bymounting them on one or both of the faces of the pellices. Normally thedevices or objects are only mounted on one of the two faces of thepellicle. The devices or objects .can be mounted on a preformedpellicle, or the pellicle can be formed on top of the desiredarrangement of the devices or objects.

It may be desirable in some instances, but it is not always necessary,to use an adhesive material for the purposes of assuring a propermounting of the device or object on the pellicle. The adhesives whichmay be used in this regard include the silicone greases or siliconerubbers which are made from polydimethyl siloxane materials; vegetableoil greases; cyano-acrylate polymers; and a 50% solution of polystyrenein xylene. Embedding of the device or object in the poly-paraxylylene isdesirable when the particle size of the device or object to be supportedis of the order of about 50 to 200p. m in diameter.

The following examples are illustrative of the present invention but arenot intended as a limitation upon the scope thereof.

EXAMPLE I 1 This example relates to the preparation of a simulated iceor dust field. The particles which were to be used to simulate the dustor ice field were glass beads which were 100 to 1000p. m in diameter. Ainch X 5 inch glass plate was treated with a release agent by wiping theagent on so as to provide a thin film of the agent thereon. The releaseagent was an aqueous soap solution. Before the release agent dried, theglass beads were sprinkled onto the treated glass plate in a randompattern which covered an area of about i to 5 square centimeters. Therelease agent was allowed to air dry and the glass plate was then placedin a poly-paraxylylene coating chamber. The plate was laid flat in thechamber with the side having the glass beads thereon facing upward. Afilm of poly-monochlorinated-paraxylylene of 1000A thickness was thendeposited over the glass beads on the glass plate. Following the removalof the thus coated glass beads and glass plate from the coating chamber,a 5 inch diameter aluminum ring was attached to the polymer coated glassplate with an RTV silicone adhesive. When the adhesive cured, in about 1hour, the glass plate exterior to the ring was scored with a razorblade. The glass plate and ring were then partially submerged in tepid,about 35 to 40C., water which dissolved the release agent from betweenthe para-xylylene polymer and the glass plate thus allowing thepoly-para-xylylene to be removed from the glass plate and water whilesuspended on the aluminum ring. The glass beads, which were also polymercoated, were now incorporated into the pellicle in the same randompattern configuration in which they were applied to the glass plate. Theglass beads covered about 2% of the face of the pellicle to which theywere attached.

A second simulated dust field was prepared as described above usingparticles of sand instead of the glass beads. The sand was deposited ina random fashion on the glass plate over an area of about l to 5 cm, andthe sand particles covered about 2% of the face of the pellicle on whichthey were supported.

A third simulated dust field was made as described above from glassbeads and by applying thereto a polymeric film of thepoly-monochlorinated-para-xylylene which was about 2.5;; m thick.

In FIG. 1, of the drawings, there is shown pellicle l which hasdispersed thereon the particles of sand or glass 2 which may be used toform the simulated dust field.

In FIG. 2 there is shown a cross section of the thin film of thepellicle 1a which supports the glass bead or sand particle 2a thereon.In this embodiment of the invention, the para-xylylene polymer isdeposited on the glass beads or sand particles and the film covers andenvelopes all but that portion of the glass bead or sand particle whichis resting on the glass plate on which the supported glass or sandparticles were first deposited as described above.

EXAMPLE II A para-xylylene polymer pellicle was made as described inExample I except that no glass beads or sand particles were applied tothe release agent beforehand. Following the formation of the pellicle,glass beads to 1000p. m in diameter were partially submerged in apolycyano acrylate adhesive and then applied directly to one face of thepellicle before the adhesive cured. The glass beads were placed on oneface of the pellicle in an ordered fashion so as to cover about 2% ofthe supporting face of the pellicle.

After cure of the adhesive, which took place in about 5 minutes, thebeads were permanently attached to the pellicle. This is shown in FIG. 3wherein the glass bead 2b is mounted on the thin film of polymer lb withadhesive 3.

Instead ofa poly-cyano-acrylate adhesive, a 5% solution of polystyrenein xylene; or silicon grease; or vegetable grease also be used for thepurposes of bonding the glass beads to the pellicle support.

EXAMPLE III The mounted glass beads or sand particles prepared as inExamples I and II are used to simulate dust or ice fields which may beencountered during the flight of space vehicles or ballistic missiles. Aseries of up to about of such simulated dust or ice fields, 6 inches to8 inches in diameter, are mounted along the length of a IOO-foot flighttunnel. A test missile is shot down the length of the tunnel so as tocause it to impinge on, and traverse through, each of the simulatedfields or screens in succession. Laser and X-ray cameras take picturesof the missile after impingement to record the effect of the erosionthereon during the test flight.

EXAMPLE IV A reactive mass center such as a bead of lithium is formed ina pellicle as in Examples I and II above. The lithium is then removed ina predictable fashion, as by the reaction with water vapor to liberatehydrogen for the purposes of monitoring the presence of extremely smallamounts of residual water vapor in a test atmosphere.

EXAMPLE V A release agent is applied to the surface of a glass plate asin Example I, and the thus treated surface of the plate is coated with afilm of unsubstituted pxylylene polymer about 1000A thick. The glassslide is then placed in a vacuum evaporator with the polymer coatedsurface facing the evaporant sour'ce. About 30 to 50% of the surface ofthe polymer film is then coated with gold metal through a mask to athickness of about 2000A so as to form an ordered pattern of anelectronic circuit on the film of p-xylylene polymer 11. The pattern isrepresented by the four rectangular and one circular areas 12 shown inFIG. 4. The metal coated film 11 is then removed from the glass slide asin Example I and placed in the cavity of a modified electron microscopeso as to position the gold coated film between an electron beam sourceand a silicon wafer coated with an electron sensitive resist, which ispositive or negative in activity. The electron beam having an energy ofll 00 Kev is turned on and directed towards the silicon wafer throughthe gold coated film of polyp-xylylene. The gold coated film acts as anelectron beam mask which only allows the electrons to pass through thoseareas of the gold coated film which are not coated with gold with theresult that the electrons reach the electron sensitive resist on thesilicon wafter in a pattern which represents an image of the pattern ofthe gold on the mask. The resist is then processed, so as to provide thedesired pattern on the silicon wafer.

EXAMPLE VI A release agent is applied to the surface of a glass plate asin Example I, and the thus treated surface of the plate is coated with afilm of unsubstituted pxylylene polymer about 1000A thick. The glassslide is then placed in a vacuum evaporator with the polymer coatedsurface facing the evaporant source. The polymer coated surface is thencoated through a mask with nickel metal so as to provide a -1000A thickpattern of a plurality of squares of nickel which are each 1 mm in areaand which are each positioned on a 2 mm center. After being removed fromthe glass plate the nickel coated film is placed in proximity to adefined electromagnetic field. A beam of visible light is then made tobe incident upon the metal coated film at an angle of about 90 to theplane of the film. When discrete portions of the electromagnetic fieldare activated those nickel metal squares which are in proximity to theactivated portions of the electromagnetic field are deflected from theplane of film to which they are attached without disrupting theirattachment to the film. The flexibility of the film allows for thisdeflection. As a result of this deflection the incident light isreflected from the deflected nickel squares at an angle different fromthe light incident upon those nickel squares which were not deformed ordeflected out of the plane of the film. The pattern of deflected lightprovides an alpha numeric display which can be used for visual displaypurposes or computer memory purposes.

We claim:

1. An article of commerce comprising an essentially flat film ofp-xylylene polymer having a thickness of up to about 25,000 A and whollysupporting one or more discrete objects mounted on at least one facethereof, the total surface area of said objects facing said film beingless than the total surface area of the supporting face of said film,said supported objects being ohmically isolated with respect to objectsnot supported on said one supporting face.

2. An article of commerce as in claim 1 in which said film has athickness of up to about 5000 A.

3. An article of commerce as in claim 1 in which said film has a totalsurface area on each face thereof of about 2 25 mm.

4. An article of commerce as in claim 1 in which said film has a mass ofup to about 400 micrograms/cm? 5. An article of commerce as in claim 1in whic one or more objects are supported on said film so as to cover upto about of the surface of said film.

6. An article of commerce as in claim 5 in which said objects form anordered pattern on said film.

7. An article of commerce as in claim 5 in which each of said objectshas a particle size of up to about 5mm.

8. An article of commerce as in claim 7 which is a simulated ice fieldwhich covers up to about 10% of the surface of said film.

9. An article of commerce as in claim 5 in which said objects areadapted to absorb or reflect radiated energy.

10. An article of commerce as in claim 5 in which said objects areadapted to reflect light.

1. AN ARTICLE OF COMMERCE COMPRISING AN ESSENTIALLY FLAT FILM OF P-XYLYLENE POLYMER HAVING A THICKNESS OF UP TO ABOUT 25,000 A AND WHOLLY SUPPORTING ONE OR MORE DISCRETE OBJECTS MOUNTED ON AT LEAST ONE FACE THEREOF, THE TOTAL SURFACE AREA OF SAID OBJECTS FACING SAID FILM BEING LESS THAN THE TOTAL SURFACE AREA OF THE SUPPORTING FACE OF SAID FILM, SAID SUPPORTED OBJECTS BEING OHMICALLY ISOLATED WITH RESPECT TO OBJECTS NOT SUPPORTED ON SAID ONE SUPPORTING FACE.
 2. An article of commerce as in claim 1 in which said film has a thickness of up to about 5000 A.
 3. An article of commerce as in claim 1 in which said film has a total surface area on each face thereof of about > or = 25 mm2.
 4. An article of commerce as in claim 1 in which said film has a mass of up to about 400 micrograms/cm2.
 5. An article of commerce as in claim 1 in whic one or more objects are supported on said film so as to cover up to about 90% of the surface of said film.
 6. An article of commerce as in claim 5 in which said objects form an ordered pattern on said film.
 7. An article of commerce as in claim 5 in which each of said objects has a particle size of up to about 5mm.
 8. An article of commerce as in claim 7 which is a simulated ice field which covers up to about 10% of the surface of said film.
 9. An article of commerce as in claim 5 in which said objects are adapted to absorb or reflect radiated energy.
 10. An article of commerce as in claim 5 in which said objects are adapted to reflect light. 